PARK CITY, Utah -- Third-trimester abortions -- those done beyond the 28th week of pregnancy -- account for less than 1 per cent of all abortions performed in the United States each year. Only four doctors nationwide offer the procedure.

Their stories and those of their patients are told in "After Tiller," a documentary in competition at the Sundance Film Festival.

Filmmakers Lana Wilson and Martha Shane were inspired to examine the issue after the 2009 murder of Dr. George Tiller, a colleague of the doctors featured in the film.

"Our generation has really been alienated from the abortion debate in a lot of ways," said Shane, 29. "It's become a shouting match in this country and extremely polarized, so this was a chance to take a really new approach to the issue and to focus on the intimate situations and the people who are working at the centre of the storm," she said.

Doctors Susan Robinson and LeRoy Carhart came to Sundance (with security) to discuss their participation in the film. They opened up their clinics and their homes to the filmmakers in an effort to diminish misconceptions about their work and their patients.

"One of the worst misconceptions is that women make the decision to have an abortion lightly and frivolously," Robinson said. "But, actually, it turns out women are adult moral agents, just like everybody else, and they are capable of wrestling with very complex ethical issues that only they have all the pieces to."

The filmmakers acknowledge that even those in favour of abortion rights often don't support or understand third-trimester abortions. Shane and Wilson themselves didn't know much about the issue before beginning work on their film three years ago. What would motivate a woman to seek an abortion so late in her pregnancy? What would motivate physicians to perform a procedure that leads them to be vilified daily by protesters?

"One of the things that most surprised us about getting to know (the doctors) is they're not political zealots," Wilson said. "They have very complicated feelings on this subject. They struggle with a lot of the moral and ethical complexities in doing this work every single day."

One of the doctors featured in the film said she sees the aborted infants as babies, not fetuses or clumps of cells. But the baby is inside the woman, "and she can't handle it," the doctor said, for what she described as "a variety of desperate reasons."

"First and foremost, they're doctors. They're not politicians," Shane said. "Their goal is to care for their patients who are going through one of the most difficult things a woman can go through, so that's where their dedication comes from."

The film shares the stories of several patients undergoing third-trimester abortions. Most elected to have the procedure after learning of severe fetal anomalies that would prevent their babies from living healthy lives. In such cases, the pregnancies were planned and the parents hold funerals for their stillborn infants.

One young patient, a college student, was raped and in denial about her pregnancy for months. Another spent several months saving up for an abortion, and by the time she had the money, she was more than 28 weeks pregnant.

The film shows how women often ponder their decision "for days, for weeks, some of them for months trying to get help and not being able to find it," said Carhart, a Vietnam veteran who has been providing abortions since the late 1980s.

The film also includes the protesters who regularly march and chant outside these doctors' offices and offers their arguments against the procedure.

"Abortion is not a public policy," Carhart said. "(Opponents) are using abortion for political purpose, and it's not for the betterment of the people in this country."

Shane and Wilson said they hope their film humanizes the doctors and offers a sense of "the wide-ranging circumstances" that motivate women to choose third-trimester abortions.

Wilson said viewers opposed to abortion might be "really surprised about some of these people's circumstances, especially fetal-anomaly patients, and really have to think, 'Should we be having these blanket laws applying to everyone?"'

Robinson hopes the film makes abortion easier to understand and accept -- and ultimately guarantees its accessibility.

"I hope that it will make it clear to viewers that this is a very complex topic and women consider these issues very deeply," she said. "I hope that it will help de-stigmatize the whole issue of abortion so that it's a little less cloaked in secrecy and shame. It needs to stay legal. It needs to stay safe and it needs to come out of the shadows."